The purpose of this research is to identify a valid objective method to diagnose a prevalent sleep disorder, restless legs syndrome (RLS), in elders with dementia. RLS is characterized by uncomfortable leg sensations that disturb sleep and are associated with significantly decreased health and cognitive functioning. Elders with dementia have cognitive and language deficits that prevent them from reporting sensory symptoms, and there are no valid objective measures that can diagnose RLS in them. The syndrome is likely to be present in elders with dementia because they often have RLS risk factors like iron deficiency and taking dopamine antagonists. Motor activity such as leg movement, signs of leg discomfort such as rubbing the legs, and iron deficiency may indicate RLS. An NIH conference recommended testing the validity of these RLS objective indicators in elders with dementia. Our research team used the NIH recommendations and our prior instrument development experience to develop an observational RLS measure, the Behavioral Indicators Test-Restless Legs (BIT-RL). A pilot study showed that elders with RLS and elders with dementia have high frequencies of RLS behavioral indicators on the BIT-RL. We also have shown in 102 elders with dementia that increased leg movements are predictive of reduced sleep at night in elders with dementia, indicating that leg movements may be a marker for RLS. In this study, we aim to determine the sensitivity, specificity, and cut-off values (scores on the instruments that indicate a positive diagnosis) for the BIT-RL;a measure of leg movements - the Periodic Activity Monitor-RL;and serum ferritin. We will conduct the study in elders without dementia because they can verbalize their RLS symptoms, and self-report of symptoms is the diagnostic "gold standard". Participants (n=186) who meet the RLS diagnostic criteria and those (n=186) who do not will spend 3 days and nights at the General Clinical Research Center. Blinded research assistants will conduct observations for RLS behaviors using the BIT-RL and one night of polysomnography to screen for sleep apnea. Staff at the GCRC will collect serum ferritin. Participants will wear the Periodic Activity Monitor-RL for 5 nights. A trained nurse practitioner will conduct the Johns Hopkins Structured Diagnostic Interview of RLS Symptoms and make the diagnosis of RLS positive or RLS negative. Receiver Operator Curves will determine the best single or combination of instruments to diagnose RLS.